net: skb_trim explicitely check the linearity instead of data_len

The purpose of the check on data_len is to check linearity, so use the inline
helper for this. No overhead and more explicit.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 8cac356..aeaad97 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1442,7 +1442,7 @@
 
 static inline void __skb_trim(struct sk_buff *skb, unsigned int len)
 {
-	if (unlikely(skb->data_len)) {
+	if (unlikely(skb_is_nonlinear(skb))) {
 		WARN_ON(1);
 		return;
 	}